I upgraded my computer (i7 920 3ghz) from Radeon 5850 to 6970, and I have to say that the improvement is quite big in the game. I feel that CoD is finally playable on mid settings, even I do still get some strange stutters over land and the shadows seems still to be "wiggling" or flickering all the time. However the overall experience has improved and finally getting my Track-IR this week. Really enjoying the game now.
